Syntheses,characterization and thermal properties of the lanthanide complexes with 2-mercaptonicotinic acid and 1,10-phenanthroline

Fourteen new complexes with the general formula of Ln(Hmna)₃(phen) (H₂mna = 2-mercaptonicotinic acid and phen = 1,10-phenanthroline) were synthesized and characterized by elemental analyses, IR spectra and thermogravimetric analyses. In addition, molar specific heat capacities were determined by a microcalorimeter at 298.15 K. The IR spectra of the complexes showed that the Ln³⁺ coordinated with the oxygen atoms of H₂mna and the nitrogen atoms of phen. The complexes decomposed directly to oxides Ln₂O₃, CeO₂, Pr₆O₁₁, and Tb₄O₇ in one step. The values of molar specific heat capacities for fourteen solid complexes were plotted against the atomic numbers of lanthanide, which presented as “tripartite effect”. It suggested a certain amount of covalent character existed in the bond of Ln³⁺ and ligands, according with nephelauxetic effect of 4f electrons of rare earth ions. The article is published in the original.     

Novel lanthanide complexeswith di-2-pyridyl ketone-<Emphasis Type="Italic">p</Emphasis>-chloro-benzoylhydrazone

The reaction of a hydrated nitrate salt of lanthanide(III) (Ln=Er, Ho, Tb, Gd) or yttrium(III) (Y) with the ligand di-2-pyridyl ketone-p-Cl-benzoylhydrazone (DpkClBH), afforded air stable solid compounds. The new complexes characterized by means of elemental analysis (C, H, N, Ln), magnetic moment determinations and spectroscopic data (IR, MS). It is proposed that they are cationic of the general type: [Ln(DpkClBH)₂(NO₃)₂]NO₃·nH₂O, (n=2, 1, 1, 1, 1.5 for Ln=Y, Gd, Tb, Ho, Er, respectively). Their thermal decomposition was studied in nitrogen atmosphere, between 25–980°C, by using simultaneous TG/DTG-DTA technique. The IR spectroscopy used to determine the intermediates and the final products. The anhydrous nitrate complexes decomposed to the intermediates Ln(DpkClBH)(NO₃)₂, which upon further heating give a carbonaceous residue of Ln₂O₃ at 980°C. The mass spectra revealed the molecular ions of the complexes and their possible fragmentation pattern.     

Preparation, Spectral and Thermal Studies of Y(III) and Lanthanide(III) 1-Hydroxy-2-Naphthoates

Complexes of lanthanide(III) (La–Lu) and Y(III) with 1-hydroxy-2-naphthoic acid were obtained as crystalline compounds with a general formula Ln[C₁₀H₆(OH)COO]₃⋅nH₂O:n=6 for La–Tm and Y, n=2 for Yb and n=0 for Lu. IR spectra of the prepared complexes were recorded, and their thermal decomposition in air were investigated. Spectroscopic data suggest that in the coordination of metal-organic ligand only oxygen atoms from the carboxylate group take part. When heated, the complexes decompose to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇ with intermediate formation of Ln(C₁₁H₇O₃)(C₁₁H₆O₃). This revised version was published online in August 2006 with corrections to the Cover Date.     

Spectral and Thermal Studies of Rare Earth Complexes With 2,4,6-trimethylbenzoic Acid

The rare earth element 2,4,6-trimethylbenzoates were prepared as solids with the general formula Ln(C₁₀ H₁₁ O₂ )₃ ×n H₂ O, where n =2 for Ln =Y, La–Nd, and n =1 for Ln =Sm–Lu. The IR spectra of the complexes prepared were recorded and their solubilities in water and thermal decomposition in the air were investigated. During heating the hydrated complexes lose all the crystallization water molecules in one (Y, Ce–Lu) or two steps (La) and then the anhydrous complexes decompose either directly to oxides (Y, Ce, Pr, Sm–Lu) or with intermediate formation oxocarbonates Ln₂ O₂ CO₃ (La, Nd). The carboxylate groups in the complexes prepared act probably as mono- and bidentate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal,spectral and magnetic behaviour of 4-chloro-2-methoxybenzoates of light lanthanides(III)

4-Chloro-2-methoxybenzoates of light lanthanides(III) were obtained as mono-, di-or trihydrates with metal to ligand ratio of 1:3 and general formula Ln(C₈H₆ClO₃)₃·nH₂O, where n=1 for Ln=Ce, Pr, n=2 for Ln=Nd, Sm, Eu, Gd and n=3 for Ln=La. The complexes were characterized by elemental analysis, IR spectra, thermogravimetric studies, X-ray diffraction and magnetic measurements. The carboxylate group appears to be a symmetrical bidentate, chelating ligand. All complexes seem polycrystalline compounds. Their thermal stabilities were determined in air. When heated they dehydrate to form anhydrous salts which next are decomposed to the oxides of the respective metals. The solubilities of light lanthanide(III) 4-chloro-2-methoxybenzoates in water at 293 K are of the order of 10⁻⁵ mol dm⁻³. The magnetic moments were determined over the range of 77–300 K. They obey the Curie-Weiss law. The values of μ_eff calculated for all compounds are close to those obtained for Ln³⁺ by Hund and Van Vleck. The results indicate that there is no influence of the ligand field of 4f electrons on lanthanide ions and the metal ligand bonding is mainly electrostatic in nature.     

4-Chloro-2-methoxybenzoates of heavy lanthanides(III) and yttrium(III)

4-Chloro-2-methoxybenzoates of heavy lanthanides(III) and yttrium(III) were obtained as mono-, di-, tri-or tetrahydrates with metal to ligand ratio of 1:3 and general formula Ln(C₈H₆ClO₃)₃·nH₂O, where n=1 for Ln=Er, n=2 for Ln=Tb, Dy, Tm, Y, n=3 for Ln=Ho and n=4 for Yb and Lu. The complexes were characterized by elemental analysis, FTIR spectra, TG, DTA and DSC curves, X-ray diffraction and magnetic measurements. The carboxylate group appears to be a symmetrical bidentate chelating ligand. All complexes are polycrystalline compounds. The values of enthalpy, ΔH, of the dehydration process for analysed complexes were also determined. The solubilities of heavy lanthanide(III) 4-chloro-2-methoxybenzoates in water at 293 K are of the order of 10⁻⁴ mol dm⁻³. The magnetic moments were determined over the range of 76–303 K. The results indicate that there is no influence of the ligand field of 4f electrons on lanthanide ions and the metal ligand bonding is mainly electrostatic in nature.     

Synthesis And Characterization Of Complexes Of Rare Earth Elements With 1,1-Cyclobutanedicarboxylic Acid

The complexes of yttrium and lanthanide with 1,1-cyclobutanedicarboxylic acid of the formula: Ln₂(C₆H₆O₄)₃⋅nH₂O, where n=4 for Y, Pr–Tm, n=5 for Yb,Lu, n=7 for La, Ce have been studied. The solid complexes have colours typical of Ln³⁺ ions. During heating in air they lose water molecules and then decompose to the oxides, directly (Y, Ce, Tm, Yb) or with intermediate formation. The thermal decomposition is connected with released water (313–353 K), carbon dioxide, hydrocarbons(538–598 K) and carbon oxide for Ho and Lu. When heated in nitrogen they dehydrate to form anhydrous salt and next decompose to the mixture of carbon and oxides of respective metals. IR spectra of the prepared complexes suggest that the carboxylate groups are bidentate chelating. This revised version was published online in August 2006 with corrections to the Cover Date.     

2D l‐Di‐toluoyl‐tartaric acid Lanthanide Coordination Polymers: Toward Single‐component White‐Light and NIR Luminescent Materials

A series of five l ‐di‐p‐toluoyl‐tartaric acid (l ‐DTTA) lanthanide coordination polymers, namely {[Ln₄K⁴ L₆(H₂O)_x]?yH₂O}_n, [Ln=Dy ( 1 ), x=24, y=12; Ln=Ho ( 2 ), x=23, y=12; Ln=Er ( 3 ), x=24, y=12; Ln=Yb ( 4 ), x=24, y=11; Ln=Lu ( 5 ), x=24, y=12] have been isolated by simple reactions of H₂L (H₂L= L ‐DTTA) with LnCl₃?6 H₂O at ambient temperature. X‐ray crystallographic analysis reveals that complexes 1 – 5 feature two‐dimensional (2D) network structures in which the Ln³⁺ ions are bridged by carboxylate groups of ligands in two unique coordinated modes. Luminescent spectra demonstrate that complex 1 realizes single‐component white‐light emission, while complexes 2 – 4 exhibit a characteristic near‐infrared (NIR) luminescence in the solid state at room temperature.     

Thermal and spectral studies of rare earth element 3-methoxy-4-methylbenzonates

3-Methoxy-4-methylbenzoates of Y(III) and lanthanide(III) (La-Lu) were prepared as crystalline compounds with molar ratio of metal to organic ligand of 1.0:3.0 and general formula Ln(C₉H₉O₃)3·nH₂O, where n=2 for Y, La-Er and n=0 for Tm-Lu. IR spectra of the prepared complexes suggest that carboxylate groups are bidentate chelating. During heating dihydrated complexes lose crystallization water molecules in one (Y, La, Pr-Er) or two steps (Ce) and then all the anhydrous complexes decompose directly to oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇.Vadim Mamleev is grateful to Region Nord-pas-de-Calais (France) for financial support and to laboratory PERF of ENSCL for its kind invitation to continue the joint work on thermal analysis.     

Thermal behavior and other properties of Pr(III), Sm(III), Eu(III), Gd(III), Tb(III) complexes with 4,4′-bipyridine and trichloroacetates

A novel mixed-ligand complexes with empirical formulae: Ln(4-bpy)_1.5(CCl₃COO)₃·nH₂O (where Ln(III) = Pr, Sm, Eu, Gd, Tb; n = 1 for Pr, Sm, Eu and n = 3 for Gd, Tb; 4-bpy = 4,4′-bipyridine) were prepared and characterized by chemical, elemental analysis and IR spectroscopy. Conductivity studies (in methanol, dimethylformamide and dimethylsulfoxide) were also described. All complexes are crystalline. The way of metal–ligand coordination was discussed. The thermal properties of complexes in the solid state were studied under non-isothermal conditions in air atmosphere. During heating the complexes decompose via intermediate products to the oxides: Pr₆O₁₁, Ln₂O₃ (for Sm, Eu, Gd) and Tb₄O₇. TG-MS system was used to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolysis of Pr(III) and Sm(III) compounds in air.     

Thermal and spectroscopic investigations of new lanthanide complexes with 1,2,4-benzenetricarboxylic acid

The new 1,2,4-benzenetricarboxylates of lanthanide(III) of the formula Ln(btc)·nH₂O, where btc is 1,2,4-benzenetricarboxylate; Ln is La-Lu, and n=2 for Ce; n=3 for La, Yb, Lu; and n=4 for Pr-Tm were prepared and characterized by elemental analysis, infrared spectra and X-ray diffraction patterns. Polycrystalline complexes are isotructural in the two groups: La-Tm and Yb, Lu. IR spectra of the complexes show that all carboxylate groups from 1,2,4-benzentricarboxylate ligands are engaged in coordination of lanthanide atoms. The thermal analysis of the investigated complexes in air atmosphere was carried out by means of simultaneous TG-DTA technique. The complexes are stable up to about 30°C but further heating leads to stepwise dehydration. Next, anhydrous complexes decompose to corresponding oxides. The combined TG-FTIR technique was employed to study of decomposition pathway of the investigated complexes.     

Self-Assembly of Isopolyanion Clusters and Lanthanide-Organic Units into 2D Layers: (NH4)2{[Ln2(C7H4NO4)2(H2O)9][(H2W12O40)]}·nH2O (Ln?=?Gd, Tb, Ho)

Three novel 1:2 composite compounds prepared with the isopolyanions and lanthanide-organic units, (NH₄)₂{[Ln₂(HL)₂(H₂O)₉][(H₂W₁₂O₄₀)]}·nH₂O (Ln = Gd³⁺ (1), Tb³⁺ (2), n = 15; Ho³⁺ (3), n = 10; L = pyridine-3,5-dicarboxylate) were synthesized at room temperature and characterized by routine methods. X-ray structural analysis reveals that these structures are isomorphic: two crystallographically independent Ln³⁺ ions (Ln1 and Ln2) locate in different coordination environments; two ligands plays dissimilar coordination mode; the isopolyanion cluster acts as a tridentate ligand and connects three Ln³⁺ ions (Ln1, Ln1′ and Ln2) forming an unusual 2D undee-layer. The room temperature luminescent of 2 has been studied and exhibits a Tb³⁺ characteristic emission in the range of 450–650 nm.     

Thermal and Spectral Studies of Y(III) and Lanthanide(III) Complexes with Mesaconic Acid

Y(III) and lanthanide(III) mesaconates were prepared as crystalline solids with general formula Ln₂(C₅H₄O₄)₃⋅nH₂O, where n=7 for La−Pr, n=4 for Y,Nd−Ho, n=8 for Er−Lu. IR spectra of the prepared mesaconates suggest that carboxylate groups are bidentate bridging anf chelating. During heating the hydrated complexes are dehydrated in one (Y, Nd−Lu) or two steps (La−Pr) and then decompose directly to oxides (Y, Ce, Pr, Sm, Gd−Lu) or with intermediate formation Ln₂O₂CO₃ (La, Nd, Eu). This revised version was published online in August 2006 with corrections to the Cover Date.     

Application of rotate-bomb calorimeter for determining the standard molar enthalpy of formation of Ln(Pdc)3(Phen)

Thirteen solid ternary complexes Ln(Pdc)₃(Phen) (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu;) have been synthesized in absolute ethanol by rare-earth element chloride low hydrate reacting with the mixed ligands of ammonium pyrrolidinedithiocarbamate (APdc) and 1,10-phenanthroline · H₂O (o-Phen · H₂O) in the ordinary laboratory atmosphere without any cautions against moisture or air sensitivity. IR spectra of the complexes showed that the Ln³⁺ ion was coordinated with six sulfur atoms of three Pdc⁻ and two nitrogen atoms of o-Phen · H₂O. It was assumed that the coordination number of Ln³⁺ is eight. The constant-volume combustion energies of the complexes, Δ_c U, were determined by a precise rotate-bomb calorimeter at 298.15 K. Their standard molar enthalpies of combustion, Δ_c H _m ^o , and standard molar enthalpies of formation, Δ_f H _m ^o were calculated. The text was submitted by the authors in English.     

Thermal behaviour of hydrated lanthanide complexes with heptanedioic acid

The multi-step dehydration and decomposition of trivalent lanthanum and lanthanide heptanediate polyhydrates were investigated by means of thermal analysis completed with infrared study. Further more, X-ray diffraction data for investigated heptanediate complexes of general stoichiometry Ln₂(C₇H₁₀O₄)₃.nH₂O (wheren=16 in the case of La, Ce, Pr, Nd and Sm pimelates,n=8 for Eu, Gd, Tb, Dy, Er and Tm pimelates,n=12 for Ho, Yb and Lu pimelates) were also reported.

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Zusammenfassung Mittels TG, DTG, DTA wurde in Verbindung mit IR-Methoden der mehrstufige Dehydratations- und der Zersetzungsvorgang der Polyhydrate der PimelinsÄuresalze von dreiwertigem Lanthan und dreiwertigen Lanthanoiden untersucht. Röntgendiffraktionsdaten der untersuchten Heptandiat-Komplexe mit der allgemeinen Formel Ln₂(C₇H₁₀O₄)₃ nH₂O (mitn=16 für Ln=La, Ce, Pr, Nd und Sm,n=8 für Ln=Eu, Gd, Tb, Dy, Er und Tm sowien=12 für Ln=Ho, Yb und Lu) werden ebenfalls gegeben.

     

Synthesis,structure, and photophysical property of series of Ln(III) coordination polymers with different carboxylato ligands (Ln = Sm,Eu)

Four Ln(III) coordination polymers, {[Ln₂(1,3-bdc)₃(H₂O)₄]·DMF·H₂O} _n (Ln = Sm 1, Eu 2) and [Ln₂(mal)₃(H₂O)₆] _n (Ln = Sm 3, Eu 4) (1,3-H₂bdc = isophthalate acid, H₂mal = malonate acid), were hydrothermally synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectra, UV–Vis–NIR absorption spectra, and fluorescence spectra. The structural analyses reveal that polymer 1 is a 3D coordination polymer. Its asymmetry unit contains two crystallographically independent Sm(III) ions, both are eight-coordinated. The 1,3-bdc^2? anions show three different coordination modes. The structure of polymer 2 is isomorphous with that of 1. Polymer 3 is also a 3D coordination polymer, its asymmetry unit contains one Sm(III) ion, which is nine-coordinate. The mal^2? anions have two different coordination modes. The structure of polymer 4 is isomorphous with that of 3. The luminescent study shows that polymers 1, 2, and 4 exhibit characteristic emission bands in the visible region, corresponding to the transitions of the Ln(III) ions. By comparison and analysis of luminescence, it is found that the incidence of the same ligand on the corresponding spectra of different Ln(III) ions is different, and the influence of different ligands on luminescence of the same Ln(III) ion is also very different.

     

New Complexes of Rare Earth Elements with 3-Methyladipic Acid

Rare earth element 3-methyladipates were prepared as crystalline solids with general formula Ln₂(C₇H₁₀O₄)₃⋅nH₂O, where n=6 for La, n=4 for Ce,Sm–Lu, n=5 for Pr, Nd and n=5.5 for Y. Their solubilities in water at 293 K were determined (2⋅10^–3–1.5⋅10^–4 mol dm^–3). The IR spectra of the prepared complexes suggest that the carboxylate groups are bidentate chelating. During heating the hydrated 3-methyladipates lose all crystallization water molecules in one (Ce–Lu) or two steps (Y) (except of La(III) complex which undergoes tomonohydrate) and then decompose directly to oxides (Y, Ce) or with intermediate formation of oxocarbonates Ln₂O₂CO₃ (Pr–Tb) or Ln₂O(CO₃)₂ (Gd–Lu). Only La(III) complex decomposes in four steps forming additionally unstable La₂(C₇H₁₀O₄)(CO₃)₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal decomposition of lanthanide(III) and Y(III) 3,4,5-trihydroxybenzoates: Preparation, properties

Complexes of lanthanides(III) (La-Lu) and Y(III) with 3,4,5-trihydroxybenzoic acid (gallic acid) were obtained and their thermal decomposition, IR spectra and solubility in water have been investigated. When heated, the complexes with a general formula Ln(C₇H₅O₅)(C₇H₄O₅)·nH₂O (n=2 for La-Ho and Y: n=0 for Er-Lu) lose their crystallization water and decompose to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁, and Tb₄O₇, except of lanthanum and neodymium complexes, which additionally form stable oxocarbonates such as Ln₂O₂CO₃. The complexes are sparingly soluble in water (0.3·10^–5–8.3·10^–4 mol dm^–3).This revised version was published online in November 2005 with corrections to the Cover Date.     

Thermal decomposition of 4,4′-dipyridyl complexes of light rare-earth thiocyanates in air atmosphere

The thermal decompositions of Ln(NCS)₃(4-dipy)₂·5H₂O were studied, whereLn=La, Pr, Nd, Sm, Eu and Y, and 4-dipy=4,4′-dipyridyl. The compounds are first dehydrated. During the thermal decomposition of Ln(NCS)₃(4-dipy)₂, deamination takes place. The transient products decompose with the formation of Ln₂O₂SO₄. The energies of activation for the first step of dehydration of the La, Pr, Nd, Sm and Eu complexes were determined.

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Zusammenfassung Es wurde die thermische Zersetzung von Ln(NCS)₃(4-dipy)₂.5H₂O mitLn=La, Pr, Nd, Sm, Eu, Y und 4-dipy=4,4′-Dipyridyl untersucht. Die Verbindungen werden zuerst dehydratiert. Bei der thermischen Zersetzung von Ln(NCS)₃(4-dipy)₂ findet eine Desaminierung statt. Die übergangsprodukte zersetzen sich unter Bildung von Ln₂O₂SO₄. Die Aktivierungsenergie für den ersten Schritt der Dehydratation der La-, Pr-, Nd-, Sm- und Eu-Komplexe wurde ermittelt.

     

Spectral and Thermal Studies of Rare Earth Element 3-methylglutarates

Conditions for the formation of rare earth element (Y, La–Lu) 3-methylglutarates were studied and their quantitative composition and solubilities in water at 293 K were determined (10^–2 mol dm^–3). The IR spectra of the prepared complexes with general formula Ln₂(C₆H₈O₄)₃ nH₂O (n=3–8) were recorded and their thermal decomposition in the air were investigated. During heating the hydrated 3-methylglutarates are dehydrated in one step and next anhydrous complexes decompose to oxides Ln₂O₃ with intermediate formation Ln₂O₂CO₃ (Y, La, Nd–Gd) or directly to the oxides, Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇ (Ce, Pr, Tb–Lu). This revised version was published online in August 2006 with corrections to the Cover Date.